Field of the Invention
The present invention pertains to a method and apparatus for determining interfacial tension between two immiscible fluids: liquid/liquid or gas/liquid by means of a droplet of the less dense fluid surrounded by the more dense fluid, both fluids are spinning together with a glass tube. This basic physical property of fluid interface is important to most fields of technological art in chemical solutions for enhanced oil recovery.
The invention pertains to measurement of interfacial tension but is especially advantageous for measurement of all magnitudes of interfacial tension less than 1 dyn/cm (10−3 newton/meter) and is even more advantageous for measurement of interfacial tension less than 10−2dyn/cm (10−5 newton/meter) and rotation speed need to be more than 10,000 rpm. It is also advantageous for interfacial tension measurement at pressure and temperature substantially different from ambient condition.
Description of Prior Art
Conventional methods of measuring fluid interfacial tension are the force method, the shape method, and several miscellaneous methods. The spinning drop technique is a shape method, which is used to measure low interfacial tension. U.S. Pat. No. 4,250,741 teaches an instrument for measuring interfacial tension between two fluids, which is based upon spinning drop technique, one of the conventional shape methods of the known art for measuring fluid interfacial tension. This invention includes a sample tube for containing the fluids and housing for enclosing the sample tube. A massive bearing housing contains a precision ground shaft and is connected to the sample tube. The shaft is rotated by a motor causing the sample tube to rotate at the same time. However, this instrument requires specially constructed equipment and parts. Furthermore, interfacial tension measurement requires a great deal of time and skill. Last but not least, this instrument cannot provide interfacial tension measurement under high pressure and high temperature conditions.
U.S. Pat. No. 4,644,782 introduces a method and device for measuring interfacial tension between two immiscible liquids. The device comprises a transparent tubular cylinder for receiving two liquids of different densities and a rod which is mounted on the longitudinal axis of the cylinder. The cylinder is sealed at both ends. The less dense liquid will form around the rod at an appropriate speed, and when steady state equilibrium is achieved by the liquids inside the cylinder, the diameter of the less dense liquid and the rotational speed of the cylinders are measured. However, this invention cannot provide interfacial tension measurement under high pressure and high temperature conditions.
U.S. Pat. No. 5,150,607 discloses an apparatus for measuring interfacial tension between two different polymers, under conditions which keep the polymers melted, and which cause the less dense polymer form a drop of a generally cigar shape. By measuring the diameter of the drop at desired angular velocities upper and lower bounds for interfacial tension can be determined. However, this invention cannot provide interfacial tension measurement under high pressure and high temperature conditions.
It is an object of this invention to provide a simple and robust construction that does not require sophisticated technology or expensive materials for high pressure high temperature interfacial tension measurement.
It is another object of this invention to provide a practical and affordable low maintenance device for accurately measuring surface or interfacial tension between two immiscible fluids without compromising its integrity and performance.
It is another object of this invention to provide a surface or interfacial tension measurement device which requires substantially less maintenance work than other designs yet meets industry standards of accuracy, repeatability, durability, and ease of cleaning.